library.thinkquest

1. Molecules of LifeLecture 3 http://library.thinkquest.org

2. Much of the text material in the lecture notes is from our textbook, “Essential Biology with Physiology” by Neil A. Campbell, Jane B. Reece, and Eric J. Simon (2004 and 2008). I don’t claim authorship. Other sources were sometimes used, and are noted.

3. Outline • Lactose intolerance • Organic chemistry • Macromolecules • Dehydration synthesis and hydrolysis • Carbohydrates • Lipids and steroids • Proteins and amino acids • Nucleic acids • Words and terms to know • Possible test items

4. Dairy-Producing Areas http://www.nass.usda.gov Dairy products are a substantial part of the agricultural economy of the United States.

5. National Advertising Campaign http://www.alondra2005.com

6. Lactose Intolerance • Lactose is the primary sugar found in cow’s milk and other dairy products. • For some people, lactose can cause bloating, gas, and other symptoms. • They suffer from lactose intolerance, which is the inability to digest lactose. • The small intestine produces an enzyme, lactase, that breaks-down lactose so it can be absorbed. • Lactase is not produced in sufficient quantities in individuals with lactose intolerance. -ose — a sugar -ase — an enzyme

7. Symptoms and Treatment • Water balance in the small intestine is disturbed, causing uncomfortable symptoms. • Lactose intolerance cannot be reversed, although the symptoms can be controlled by: • Avoiding foods with lactose • Consuming milk and cheese substitutes made from soy • Consuming dairy products pretreated with lactase • Ingesting pills that contain lactase • This condition illustrates the importance of biological molecules for health.

8. Another National Campaign http://publicaffairs.uth.tmc.edu A campaign developed by the University of Texas.

9. Organic Chemistry • A cell is mostly water, and the rest consists of carbon-based molecules. • Carbon can form large, complex, and diverse structures. • The study of carbon-based compounds is called organic chemistry. http://organicglassware.com

10. All Life is Carbon-Based http://3611farm1.static.flickr.com http://www.rspb.org.uk http://media.wiley.com http://www.richardseaman.com http://www.fs.fed.us

11. Characteristics of Carbon • The versatility of carbon as a molecular component is the result of five features: • Has four electrons in an outer shell that can hold eight electrons. • Completes its outer shell by forming four covalent bonds with other elements. • Serves as an molecular intersection that can branch-off in four directions. • Is able to bond to other carbon atoms to form various molecular structures. • Is able to bond to other elements including hydrogen, oxygen, and nitrogen.

12. Carbon Skeletons • Carbon skeletons can vary in length from very short to very long. • They may be unbranched or branched. • They may have double covalent bonds, which can vary in location. • They may be arranged in single- and multi-ring structures. Carbon backbone of a protein molecule http://www.scielo.com

13. An Early Chemistry Laboratory All images from http://life.bio.sunysb.edu Hemiaster phillipi, an Antarctic echinoderm Voyage of the H.M.S. Challenger, 1872

14. Hydrocarbons • The simplest organic compounds are hydrocarbons consisting of carbon and hydrogen atoms. • The simplest hydrocarbon is methane (CH4), a carbon atom with covalent bonds to four hydrogen atoms. • Methane is: • One of the most abundant hydrocarbons in natural gas • Produced by prokaryotic cells that live in swamps • Produced by prokaryotic cells in the digestive tracts of grazing animals • Octane—with its eight carbon molecules—is contained in gasoline used in internal combustion engines. • The energy-rich parts of fat molecules also have hydrocarbon structures.

15. Fossil Fuels From the ancient coal forests to the gas tank http://www.versacreations.net http://www.naturenorth.com

16. Drive My Car McLaren F1 http://www.popularcars.us No matter how much of an engineering marvel, most automobiles run on long-dead plant life. http://www.adclassix.com

17. Organic Molecule Shape • Each organic molecule has a unique three-dimensional shape in part due carbon’s ability to form four bonds. • Large organic molecules can have elaborate shapes including multiple-ring structures. • Some biological molecules recognize one another based on their shapes (known as enzymes and substrates). Tetrahedral arrangement of the methane molecule http://chemlab.truman.edu

18. Molecular Comparisons Organic molecules can range from simple to very complex structures. A protein molecule http://nai.nasa.gov Methane molecule (CH4) http://fixedreference.com

19. Functional Groups • The properties of an organic compound depend on the carbon and other atoms attached to the carbon skeleton. • Groups of molecules that participate in a chemical reactions are known as functional groups. • Four functional groups important in the chemistry of life are: • Hydroxyl group (O-H), found in alcohols and sugars • Carbonyl group (C=O), found in sugars • Amino group (H-N-H), found in amino acids • Carboxyl group (O=C-O-H), found in amino acids, fatty acids, and some vitamins • Biological molecules often contain two or more different functional groups.

20. Macromolecules • Biological molecules that are very large (on a molecular scale) are known as macromolecules. • Macromolecules include: • Polysaccharides (complex sugars) • Proteins • The nucleic acids, DNA and RNA • The structures of many macromolecules consist of polymers—they are synthesized many smaller molecules known as monomers. • A polymer is like a beaded necklace consisting of many individual beads.

21. Polymers Computer-generated graphic http://www.accelrys.com A polymer chain

22. Polymer Formation • Polymers are formed from monomers through the biochemical process known as dehydration synthesis. • For each monomer added to the polymer chain, a water (H2O) molecule is formed through release of one oxygen and two hydrogen molecules. • The monomers replace the lost covalent bonds from the lost H2O with a bond to each other.

23. Dehydration Synthesis (Happy Face Version) (H2O) http://chsweb.lr.k12.nj.us Monomers are joined through the process of dehydration synthesis.

24. Break-down of Polymers • Organisms not only make molecules but they can also break them down. • Starches and proteins in foods consist of long polymers. • Polymers must be digested to make the monomers available to the body’s cells. • The process is known as hydrolysis—it reverses the process of dehydration synthesis. • Bonds between monomers are broken by adding water, which is facilitated by an enzyme to promote the reaction. • The double-molecule sucrose (also known as table sugar) is hydrolyzed in the small intestine.

25. Hydrolysis Maltose + Enzyme Glucose Glucose http://northonline.sccd.ctc.edu Molecular chains are broken-down through hydrolysis

26. Carbohydrates http://www.blackgoldpotatoes.com http://www.dormgear.com Carbohydrates range from the small sugar molecules in soft drinks to long starch molecules (polymers) found in pasta and potatoes.

27. Monosaccharides • Simple sugars, or monosaccharides, include: • Glucose in sports drinks • Fructose in fruit • Glucose in corn syrup • Fructose and glucose in high fructose corn syrup (HFCS) • Glucose and fructose are isomers that have the same molecular formula (C6H12O6) —they differ in their molecular configurations. • Glucose in particular is a main fuel molecule for performing cellular work. • Fructose is much sweeter than glucose due to the slight difference in its molecular shape. • Many monosaccharides form ring-like structures in aqueous solutions.

28. Ball-and-Stick Model http://www.biology.clc.uc.edu Glucose molecular formula: C6H12O6

29. Disaccharides • A disaccharide is a double sugar formed from two monosaccharides through dehydration synthesis. • Disaccharides include: • Sucrose = glucose + fructose (sugar cane, beet sugar) • Lactose = glucose + galactose (dairy products) • Maltose = glucose + glucose (beer, malted milk shakes, milk balls) • Sucrose is the main carbohydrate found in plant sap—it is formed in the Calvin cycle, as we will discuss in another lecture.

30. Commonly-Consumed Sugars

31. Sugar Cane http://www.texasbeyondhistory.net Sugarcane and sugar beets contain sucrose—glucose and fructose form this disaccharide.

32. Sugar Cane Processing http://www2.dpi.qld.gov.au Costa Rica http://jrscience.wcp.muohio.edu

33. Sugar Beets http://farmstats.degfra.gov.uk http://www.historycooperative.org http://www.girr.org

34. Corn http://www.smm.org Corn syrup is made from glucose industrially converted to the monosaccharides, glucose and fructose.

35. Fruit Apple Trees, Nagano, Japan http://www.rei.org Fruits contain fructose—the molecules are monosaccharides

36. Honey http://www.agr.state.il.us http://chat.carleton.ca Honey contains glucose and fructose—the molecules are monosaccharides

37. Polysaccharides • Polysaccharides are long chains of single types of sugar molecules (much like pearls on a necklace). • Starch—found in roots and other plant organs—consists of many glucose monomers strung together. • Plant cells store starch in granules for a chemical source of energy and materials for building other molecules. • Starch in human diets includes potatoes, and grains such as wheat, corn, and rice. • Humans and other animals digest starches by hydrolyzing the chemical bonds between glucose molecules.

38. String of Pearls http://k43.pbase.com Somewhat analogous to identical monomers bonded together such as glucose molecules in starch.

39. Glycogen • Humans and animals store excess sugars as glycogen, a polysaccharide. • Glycogen is similar in structure to most starches, although it is extensively branched. • Glycogen is stored in granules in liver and muscle cells. • The glycogen molecules are hydrolyzed to release glucose when needed for energy. • This process is the basis for ‘carbo loading’ of eating carbohydrate-rich food the night before an athletic event.

40. Carbo Loading http://contents.answers.com http://jenyu.net

41. Cellulose • Cellulose is the most abundant organic compound—it forms cable-like fibers in the cell walls that enclose plant cells. • Cellulose, along with lignin, are major components of wood in trees. • Glucose monomers in cellulose are linked in more complex structures than in starches. • These complex molecules cannot be digested by most animals, and therefore it passes through the digestive tract as fiber or roughage. • Fiber is obtained from fruits, vegetables, whole grains, bran, and beans.

42. Molecular Structure http://www.lsbu.ac.uk Cellulose is formed from a complex array of glucose molecules.

43. Cellulose’s Properties • Grazing animals such as cows and wood-eating insects such as termites have prokaryotes (bacteria) in their digestive systems that can breakdown cellulose. • Cellulose does not readily dissolve in water, unlike sugars such as glucose and sucrose. • Like other carbohydrates, cellulose is hydrophilic, which gives a bath towel its absorbent properties. http://www.xy-towel.com

44. Lipids • Lipids are a diverse set of biological molecules including fats, cholesterol, and steroids. • They are hydrophobic—that is, they do not mix well with water because of their chemical properties. • In oil-and-vinegar salad dressings the oil—a lipid—will separate from the vinegar consisting mostly of water. http://www.tivolihome.com

45. Fats • Dietary fat consists of a glycerol molecule joined with three fatty acid molecules through dehydration synthesis. • Fatty acids consist of long hydrocarbon chains that store substantial energy—a pound of fat contains over twice the energy of a pound of starch. • Fat is stored in adipose cells that swell and shrink with the deposit and withdrawal of fat. • A reasonable amount of fat is normal and healthy as a fuel reserve. • Due to its energy efficiency, fat is difficult to burn-off for losing weight.

46. Unsaturated and Saturated Fatty Acids • A fatty acid will bend when a double covalent bond occurs in its carbon backbone. • A fatty acid is ‘unsaturated’ when it has a double bond and less than the maximum number of hydrogen atoms. • A fatty acid is ‘saturated’ when it has no double bonds and therefore the maximum number of hydrogen atoms.

47. Molecular Structures http://telstar.ote.cmu.edu http://www.ratical.org Note the linear shape in saturated fatty acids

48. ‘Decoding’ of Nutritional Fats • An ‘unsaturated fat’ has a double bond in one fatty acid chain. • A ‘polyunsaturated fat’ has double bonds in two or more fatty acid chains. • A ‘saturated fat,’ has no double bonds in any of its fatty acid chains.

49. Unhealthy Effects • Most animal fats—including lard and butter—are high in saturated fats. • The linear shape of the hydrocarbon chains in saturated fatty acids allow them to stack easily, making saturated fats solid at room temperature. • Diets rich in saturated fats can contribute to cardiovascular disease of a condition known as atherosclerosis. • Lipid-containing deposits (known as plaques) build up in the walls of the arteries, reducing blood flow and increasing the risk of heart attacks and strokes. • Many health specialists recommend avoiding foods with hydrogenated or partially hydrogenated oils.

50. Healthier Alternatives • Plant and fish fats are relatively high in unsaturated acids. • The bent shape of unsaturated fatty acids makes them less likely to form solids at room temperatures. • Unsaturated fats include corn oil, canola oil, and cod liver oil—all can be part of a healthy diet. • Tropical plants oils, such as cocoa butter, contain both unsaturated and saturated fats.